CopyBridge

Universal clipboard for Mac and Windows, built local-first.

Copy text or an image on one computer. Paste it on the other. No account, no cloud, no Telegram workaround.

CopyBridge is an early prototype. It already works for local text and image clipboard sync, but it is not packaged as a production installer yet.

Why

Mac has Universal Clipboard inside the Apple ecosystem. Windows has its own clipboard sync. People who use a Mac laptop and a Windows desktop still end up sending snippets through messengers, notes, email, or cloud drives.

CopyBridge focuses on one narrow job: make Mac <-> Windows clipboard sync feel invisible on the same local network.

What works now

• Electron app for macOS and Windows.
• Menu bar / tray background behavior.
• Plain text clipboard sync.
• Copied image clipboard sync.
• Local WebSocket transport.
• Automatic local-network discovery through mDNS.
• Silent reconnect to the last successful device.
• Encrypted clipboard payloads after devices exchange public keys.
• First-pairing verification with a matching short code.
• Echo protection so clipboard values do not bounce forever.
• Activity log, device status, sync toggle, and diagnostics copy.
• Manual host:port fallback for networks where discovery is blocked.

MVP boundary

CopyBridge currently syncs:

• text;
• copied images.

It intentionally does not support:

• files;
• clipboard history;
• accounts;
• cloud relay;
• mobile devices;
• packaged .dmg / .exe installers.

Install for development

npm install
npm start

Run the same project on both computers. Keep both devices on the same local network.

On Windows, allow local network access if the firewall asks.

Simulate two devices on one Mac

npm run start:a
npm run start:b

start:a launches a fake Mac node on port 47631. start:b launches a fake Windows node on port 47632 and connects to the first one.

Checks

npm test

Individual checks:

npm run check
npm run test:network
npm run test:secure
npm run test:trusted
npm run test:remembered
npm run test:image
node experiments/discovery-test.js

Security model

Clipboard payloads are encrypted after devices exchange public keys. New devices must be confirmed with a matching short verification code before clipboard sync starts.

Known limitations

• Local network only.
• mDNS can be slow or blocked on guest Wi-Fi, corporate networks, VPN-heavy setups, or restrictive routers.
• Manual host:port fallback exists for diagnostics, not as the intended everyday flow.
• Files are not supported yet.
• Installers are not built yet.

Roadmap

• Package macOS .dmg and Windows installer.
• Improve first-run onboarding.
• Add a short demo GIF for the README.
• Test across more Windows 11 network configurations.
• Consider optional file transfer after text and image sync are stable.

Product principle

CopyBridge should feel like "install once and forget it." The main UI is only a status panel. The product should not require settings for normal use.

License

MIT